In a typical prior art vane-type cam phaser, a controllably selective locking pin is slidingly disposed in a bore in a rotor vane to permit rotational locking of the rotor to the stator (or sprocket wheel or pulley) under certain conditions of operation of the phaser and engine. In older prior art phasers, it is desired that the rotor be locked at an extreme of the rotor authority, typically at the full retard position. In other prior art phasers, it is desired that the rotor be lockable to the stator at an intermediate position in an increased rotor range of rotational authority.
A known problem in such phasers is that there is no mechanical means such as a stop to assist in positioning the rotor for locking in an intermediate position; thus, locking is not reliable.
Various approaches involving advance-direction bias springs are known in the art for assisting a rotor locking pin in finding and securing the intermediate locking position. It is known to employ dual locking pins acting in the same direction. See, for example, U.S. Pat. No. 6,779,499 B2. Manufacturing tolerances for such phasers make impractical the precise alignment of the locking pins and their respective seats for controlling lash using both locking pins. The rotary lash will be a function of the clearance between only one or the other, but not both, of the locking pins and seats. Therefore, a means must be found for providing opportunities for the lash-controlling locking pin to engage its seat.
What is needed in the art is an arrangement for reliably engaging a lash-controlling locking pin into its seat.
It is a principal object of the present invention to minimize rotational lash in a camshaft phaser.